02-Opencv 之打开一张图片，然后用鼠标切图然后显示出来

Opencv 之打开一张图片，然后通过鼠标勾画一个区域，然后在一个新窗口当中显示新的图片。

// 20160702   打开图片并用鼠标截取图片

#include   
#include   
#include   

using namespace cv;

cv::Mat org, dst, img, tmp;


void on_mouse(int event, int x, int y, int flags, void *ustc)//event鼠标事件代号，x,y鼠标坐标，flags拖拽和键盘操作的代号  
{
	static Point pre_pt = (-1, -1);//初始坐标  
	static Point cur_pt = (-1, -1);//实时坐标  
	char temp[16];
	if (event == CV_EVENT_LBUTTONDOWN)//左键按下，读取初始坐标，并在图像上该点处划圆  
	{
		org.copyTo(img);//将原始图片复制到img中  
		sprintf(temp, "(%d,%d)", x, y);
		pre_pt = Point(x, y);
		putText(img, temp, pre_pt, FONT_HERSHEY_SIMPLEX, 0.5, Scalar(0, 0, 0, 255), 1, 8);//在窗口上显示坐标  
		circle(img, pre_pt, 2, Scalar(255, 0, 0, 0), CV_FILLED, CV_AA, 0);//划圆  
		imshow("img", img);
	}
	else if (event == CV_EVENT_MOUSEMOVE && !(flags & CV_EVENT_FLAG_LBUTTON))//左键没有按下的情况下鼠标移动的处理函数  
	{
		img.copyTo(tmp);//将img复制到临时图像tmp上，用于显示实时坐标  
		sprintf(temp, "(%d,%d)", x, y);
		cur_pt = Point(x, y);
		putText(tmp, temp, cur_pt, FONT_HERSHEY_SIMPLEX, 0.5, Scalar(0, 0, 0, 255));//只是实时显示鼠标移动的坐标  
		imshow("img", tmp);
	}
	else if (event == CV_EVENT_MOUSEMOVE && (flags & CV_EVENT_FLAG_LBUTTON))//左键按下时，鼠标移动，则在图像上划矩形  
	{
		img.copyTo(tmp);
		sprintf(temp, "(%d,%d)", x, y);
		cur_pt = Point(x, y);
		putText(tmp, temp, cur_pt, FONT_HERSHEY_SIMPLEX, 0.5, Scalar(0, 0, 0, 255));
		rectangle(tmp, pre_pt, cur_pt, Scalar(0, 255, 0, 0), 1, 8, 0);//在临时图像上实时显示鼠标拖动时形成的矩形  
		imshow("img", tmp);
	}
	else if (event == CV_EVENT_LBUTTONUP)//左键松开，将在图像上划矩形  
	{
		org.copyTo(img);
		sprintf(temp, "(%d,%d)", x, y);
		cur_pt = Point(x, y);
		putText(img, temp, cur_pt, FONT_HERSHEY_SIMPLEX, 0.5, Scalar(0, 0, 0, 255));
		circle(img, pre_pt, 2, Scalar(255, 0, 0, 0), CV_FILLED, CV_AA, 0);
		rectangle(img, pre_pt, cur_pt, Scalar(0, 255, 0, 0), 1, 8, 0);//根据初始点和结束点，将矩形画到img上  
		imshow("img", img);
		img.copyTo(tmp);
		//截取矩形包围的图像，并保存到dst中  
		int width = abs(pre_pt.x - cur_pt.x);
		int height = abs(pre_pt.y - cur_pt.y);
		if (width == 0 || height == 0)
		{
			printf("width == 0 || height == 0");
			return;
		}
		dst = org(Rect(min(cur_pt.x, pre_pt.x), min(cur_pt.y, pre_pt.y), width, height));
		namedWindow("dst");

		imshow("dst", dst);
		waitKey(0);
	}
}
void main()
{
	org = imread("1.jpg");
	org.copyTo(img);

	namedWindow("img");//定义一个img窗口  
	setMouseCallback("img", on_mouse, 0);//调用回调函数  
	imshow("img", img);
	cv::waitKey(0);
}